Control mechanism



pri 29, 1941. L. cooK 2,240,244

Y CONTROL MECHANISM Filed Sept. 1, 1938 3 Sl'xeets-Sheei',A l

INVENTOR' 14a BY @mw m QM ATTORN E April 29, 1941. L COOK 2,240,244

CONTROL MEGHANISH Filed sept. A1, i938 a shuts-sheet 2 ATTORN YS April29;, 1941. L cooK 2,240,244

CONTROL MECHANISM med sept. 1, 1958A s sheets-sheet s Patented Apr. 29,1941 connor. MEcnANTsM i Lyman Cook, Foxboro, Mass., assixnorto TheFoxboro Uompany,.Foxboro, Mass., a corporation o! MassachusettsApplication september- 1, 193s, serial No. 227,990

'13 Claims.

'I'his invention relates to improvements in control mechanisms, and moreparticularly to mechanisms ofthe character adapted to translate positioninto pressure or to translatev pressure into position.

Among the general objects of the present invention may be noted theprovision of control mechanism for positioning accurately an el'ement inproportional correspondence with a control force, which is characterizedby features of simplicity of design and operation, which is relativelyinexpensive in manufacture and assembly, and which operates in improvedmanner to effect precise and accurate positioning of the element underadverse conditions of friction and like mechanical factors, working inopposition thereto. t

More specifically, the invention seeks to provide an improved andsimplied mechan'ism for accurately positioning an element responsivelyto a lcontrol force, in which the position of the element itself isutilized, jointly with the control force, to exercise control over themotive means for actuating the element, and in which the value or valuesof the force exerted by the motive means on the element is always suchas to position the element accurately and in. exact proportion to thecontrol force,.as determined by its particular setting. The presentinvention further contemplates a novel assembly of the controlmechanism, the element tobe positioned, and the motive means thereforwhich is mechanically simple and of improved design.

^ Other objects will be iri part obvious and in part hereinafter pointedout in connection with the following analysis of this invention whereinis illustrated an embodiment of the invention in de'tail. In thedrawings:

Figure 1 is a perspective of certain parts of the control mechanism ofthe present invention; Figure 2 is a part section through the valve bodyand related parts illustrated in Figure l;

Figure 3 is a section taken along line 3-3 of Figure 1;

l mechanism.

Figure 6 .isa perspective of a modiiied form of assembly;

Figurej'l is a section along line 1--1 of Figure 6;

Figure 8 is a detailed section of the strainerl 2M shown in dotted linesin Figure 1; land Figure 9 is a diagrammatic view of apparatus embodyingthe invention set up to translate position into an air pressure.

Referring to the drawings wherein like reference characters indicatelike parts throughout the several views, and particularly to theembodiment illustrated in Figures 1 -5, reference character I0designates the enclosing casing of a pneumatic or diaphragm m'otor. Thediaphragm thereof (not shown) is connected on oneside to a valve stem I3operating a valve not shown but contained in the valve body I I. On itsother side the diaphragm is connected to a rod I3a which is connected tothe top of spring I2. Thus air pressure on the top of the diaphragmpushes' down against the force of spring I2.- Thevstem I3, rod I3a andthe valve carried thereby (not shown) are representative of elements t'obe positioned responsively to a control force.

A spacing or supporting casing I4 and a .cap

"I5 secured to part Il in air-tight relation cover spring I2. Extendinglaterally from part I4 is a lhollow extension I6 cast or otherwiseformed to provide a fiat face I 1 against which is secured as by capscrews I8, the base or panel 20 of the control mechanism assembly, agasket 2| being provided therebetween to secure the parts in air-tightrelation. The hollow extension I6 and the part Il thus provide with thediaphragm casing proper a .pressure air chamber sealed to atmosphere andlocated above the diaphragmof the motor.- .The fiat face construction ofthe extension part I6 further provides a simple and convenient means formounting the base lon the motor casing, thus to provide a compactassembly.

Pressure air is supplied to the chamber above the diaphragm through abored plug screw 25,

Figures 1 and 3, which, like cap screws I 8, may f also function tosecure the base 20 to the casing extension. The plug screw 25 extendsthrough the relatively vertical leg 26 of an L-shaped boss which is castintegrally with the base 20, the leg 26 being provided with a throughbore 21 plugged at its lower end and extending in the direction 'of thelength of the leg. The bore` of the plug screw 25 is formed tocommunicate withthe bore 21 of ieg 26 and delivers into thehollow'casing A part Il.

Referring to VFigure 2, extending :into the tion `31. l closed by ascrew 43 and intermediate its -length port 53.

' barrel-shaped portion 31 ywhich extends transversely and is axiallybored as at `33 and from which depends a plate portion 33 through whichsecuring 'screws 36 pass. An arm portion 40 extends laterally from theplate portion 33.

/The depending plate portion 33 of the valve bodyis provided with spacedvertical bores, communicating with the bore 33 of the barrel por- Oneplate bore 42 has its lower end is provided with a cross port`communicating with the air inlet port 3|. The relatively leftwise platebore 45 has`its lower endl closed by another plug screw'43 andintermediate its end is provided with across port 46 communicating withthe bore 21 of 'vertical leg 26. Thus air entering through port 3| maypass`through cross port 44 into plate bore 42 of the valve body andthence through barrel bore 33 into plate bore 45, thence into cross port46 and bore 21, and

thence to the diaphragm chamber of the valve motor through the ,boredplug screw 25.

Into one end of the bore 33 of the barrel portion 31 is threaded a plugscrew 50 having an unthreaded tubular end portion terminating short `of'the other en'd of the bore. Air from the supply air bore 42 may passinto the tubular end of the plug screw, its passage therefrom to bore 45being u nder the control of oneside of a double Vvalve 52, the othersidevof which controls the waste port 53 to atmosphere. Barrel portion31 of the valve body and the valve and air passages therein thusconstitute a control head of the supply and wasteI type for controllingthe supply of pressure air to the motor, by establishing communicationbetween air passages 42, 45, or for controlling release of ,pressure airfrom the motor as when valver52 opens passage 45 to the waste Valve 52is carried by a stem 54` which is threaded so that the position of thevalve thereon may be adjusted, the stem 54 being in turn -carried by thediaphragm unit 55 whose condition of distension or collapse determines'the position of valve 52. The diaphragm unit has its fixed end platemounted on the upper end of arm of the valve body and is arrangedbetween the arm and the leftwise end of the barrel portion 31 of thebody.

Thus the flow of air to and from the motor nI0 is controlled by thevalve 52. To prevent dirt that might be in the motor l0 from passing toand interfering with the valve 5,2 when the motor is exhausted, the bore21 (Figure 8) is provided with a strainer unit 200. 'I'his strainer unitis mounted on and extends forwardly from a hollow, externallyjthreadedsupport 20|. vThe forward end of the strainer 200 is closed by acap 202 so that the air in passing from one end'of the bore 21 to theother end thereof passes through the strainer and through the hollowsupport 20|. As shown in Figure 8, the strainer and its associated partsmay be inserted through an enlarged bore 203 at the end of the bore 21and which bore 203 is normally plugged by a plug screw 204.

Referring to Figure 2, pressure air from the inlet 3| also passes tobore 58 in the horizontal boss-leg 30, through a restriction 58a in aplug screw 53 which also closes both ends of the bore 53. Into bore 53is connected a tube 60 which connects with the interior of the diaphragmthrough a passage 6I formed in the arm 40 of the valve body. rIube 60also connects witha tube 62 (Figure 1) carrying at its end the nozzleelement 63 of a control couple of the nozzle and iiapper type. Theassociated dapper 64 is pivotally carried at its lower end by a bracket65 ,Secured to the arm 40 of the valve body and is so biased by a spring66 (shown largely in dotted lines) related to its pivot 61 that itsupper free end tends to approach the nozzle 63. The fiapper in movingagainst the nozzle varies the pressure back of the nozzle and in thediaphragms 55. 'I'he force of spring 66 may be adjusted through theadjusting nut 33.

Movement of the apper 64 in a clockwise direction .(Figure 1) is causedby movement of the arm 10 in a counterclockwise direction about itsfulcrum 1|. The arm 10 carries at its relatively lower free end anin-struck tongue 12a having edge contact with the flat face of theiiapper 64 and so arranged that it engages the flapper adjacent the endof the latter'and on the same side of the pivot 31 as the nozzle 63.

The arm 10 constitutes an element or second arm of a movementassemblywhich functions responsively both to the positioning of the rod13a and to the control force in determining the position of iiapper 64.In addition to the arm 10, this assembly includes a U-shaped cross link12; one leg of which is flxedly secured in angular relation to the arm10 by a micrometer adjusting screw 10a which provides for adjustment ofthe angular relation. 'I'he other leg of the cross link is xedly securedto the long first arm 13 of the vmovement assembly. Flapper engaging arm10, Lcross link 12, and long arm 13 thus operate as a bell crank havinga pivoting axis extending through the spaced ears 15 (one of which isshown in full lines and the other in dotted lines) extending from. theplate 16. 'Ihe previously referred to fulcrum 1| falls on this axis.

The free end of the arm 13 of the movement assembly extends relativelydownwardly for moving responsively to the position of rod |3a. l To thisend, another bell crankgassembly is provided, one arm 30 of whichoperates in the motor casing part |4 and the extension I6 thereof,its'free end engaging on a collar 3| carriedk by the rod |3a. The crossshaft V32, in the nature of an axle on which the bell crank may turn,extends through an air-tight journal bushing 83 threaded into theflat-faced wall |1'of the casing part I6. At its other end, whichextends beyond the relatively outer face of the base 20, the shaft 82carries a block 34 to which is secured an upwardly extending lever 35.The lever is provided with a longitudinally extending slot as at 36, andscrews 31 extend through the slot into the block, thus to secure thelever in desired adjusted position. 'The free; upper end of the lever isturned over as at 33. an edge thereof being provided with a notch inwhich is slidably received tle edge portion of the lower end of the arm13 of the movement assembly. A spring secured .to a fixed point 3| ofthe base 20 and the approximate mid-portion of the arm 13 urges the freeend of arm 13 into yielding engagement with the v notched lever 35. andthrough the bell crank. of which lever 65 is a part, exerts yieldingpressure in a downward direction on arm 00, thus insuring that this armfollows the position of the rod I3a. Accordingly, the bell crankmeasures the position of the valve stem I3 and positions the free end ofarm I3 of the movement assembly in proportional correspondencetherewith.

The fulcrum end of the movement assembly is positioned in accordancewith a control force which is preferably provided by a regulated airpressure delivered to a hydron 95- through either of the control airinlet openings 96, 91 in the base 20 (Figure 4). Opening 96 is shown asplugged,

' air pressure thus entering opening 91 and being delivered to theinterior of the hydron element through a passage 96 (Figure 1) formed ina mounting lug 99 extending from the relatively front face of the base26. Also extending from the base and spaced from the lug 99 is acompanion lug I forming an abutment for the spring IOI which reactsagainst the movable end plate associated with the hydron element ofwhich the previously referred to plate 'I6 is an 4extension. Thecompanion lug I00 is also provided with a passage similar to the airpassage 98, but plugging of inlet opening 96 closes oif this latterpassage.

A regulated air pressure delivered to the hydron element 95 thus causesdistension thereof against the force of spring IOI, this distensionbeing directly proportional to theh air pressure delivered to thehydron. v As the hydron is distended, there results a frictionlesssetting of the hydron end plate 16 and hence 0f the pivoting axisextending through the connections or fulcrum 'II about which themovement assembly is turnable. It will be seen further that for everyvalue of control vpressure delivered to the hydron element, the fulcrumend of the movement assembly takes up a particular position directlyrelated thereto.

By the above described arrangement the movement assembly functions tocorrelate stem position with the control pressure according to a xedrelationship. 'I'hus a' particular control pressure in the hydron 95positions the pivoting e axis of the movement assembly. Upon thisposition being established, arm l0 of the assembly acts through theflapper 64, the nozzle 63, and the valve 52 to supply air through thecontrol head to the diaphragm motor at such pressure value or values asmay be necessary to move the stem I3 until its positionas measured bythe bell crank arm 80, and hence the position of the free end of the arm13, is in the position required by the xed relationship. The combinedmovements of the bell crank moved by the valve stem and the fulcrummoved by the hydron are correlated by the nozzle ilapper and theresultant action Ais always. such as to keep the nozzle and apper withinan operative relation which allows for a variation in the order of only.001 inch at the flapper.

Referring to Figure 5, a complete operation of the instrument operatingas a valve positioning device may be traced as follows: Assuming, rst,that the pressure existing in the bellows 95 is constant and that thevalve motor I0 has positioned the element I3 to bring the movementassembly into operating relationship with respect to the nozzleand'ilapper 63, 64 (to' accomplish this the motor will have moved theelement I3 until the apper 64 is just tangent to the nozzle)-assumingthe above, now assume that the pressure in the bellows 95 is increased.'This causes the free end of the bellows to expand to the right againstthe pressure of the spring III and to position the rack 15 to the rightof its previous position. This causes. the lever or arm I0 to also moveto the right and to pivot about the axis 1I and also tends to move theilapper 64 to the right and clockwise about its axis 61. thereby tendingto uncover the nozzle 63.- As this action of the movementassembly takesplace, the lever I3 tends to pivot about its point of engagement withthe lever 66 as an axis. But as the flapper 6I tends to move away fromthe nozzle 63, the pressure in back of the nozzle starts decreasing andthe bellows 55 starts collapsing to move the valve 52 to the left,thereby restricting further escape of air from the valve motor and fromthe air inlet 3| and 32, so that the air pressure in the passageway 45,46, 21,- 25 and in the housing I6 starts building up higher than it wasbefore,'which causes the diaphragm to start pushing down against theaction of the spring I2, so that the stem I3 starts moving downwardly.As the stem I3 starts moving downwardly, the free end of the followinglever y clockwise direction to follow the movement of' the valve stem orelement I3. This counterclockwise movement of the lever is followedunder the inuence of the spring by the long arm 'I3 of the movementassembly, so that the long arm 13 is given a motion in a clockwisedirection and the short arm 'I0 is likewise given a movement in aclockwise direction, causing the ilapper 64 to tend to approach thenozzle 63 and thereby starting the pressure in the bellows 55 to buildup to move the valve 52 to the right to reduce the'lamount of airpressure then being supplied to .the motor. This action of the short arm10 on the flapper 64 and the influence of the valve stem I3 continuesuntil the valve stem I3'is brought to a position in which the short arm'I0 is so positioned as to maintain the iiapper just tangent to thenozzle.

These actions and reactions take place rapidly f and quickly balance outto position the valve stem in correspondence with the position of themovement assembly as determined by the value of the pressure in thebellows 95.

If it is assumed that the pressure in the bellows is decreased, then theabove described action takes place in the reverse. with the air pressuresupplied to the valve motor being decreased instead of increased.

Under certain conditions of installation, it is .l

necessary or desirable to reverse the action of the hydron assembly. Tothis end the .hydron assembly and the spring IOI may be removed from themounting lugs 99, I00 and its position reversed from that shown. Uponmounting the hydron assembly and spring in the reverse position, airpressure may be delivered to the interior vof the hydron through the airinlet'96 and in this instance air inlet 91 is plugged Reverse actuationof the hydron to establish the setting of the axis on which the movementassembly turns accordingly results.

In addition to the surety and precision of action which the abovedescribed construction provides, its mechanical design and arrangementare such to make for inexpensive manufacture and ease in assembly. 'I'hemounting of the control head and the control means associated therewithon a single base into which all air connections are made and thesecurement of the base to the valve motor casing without substantialmodication of the latter represents an exceedingly compact andsimplified design. The construction of the valve body and the Provisionof air passages in the legs 20, 30, reduce to a minimum the necessityfor pipe and tube connections with their consequent tendency to leak.Restrictions in the air passages are also substantially done away withand consequently the parts are permitted to respond to the varyingpressures and movements without objectionable over-shooting or hunting.

Further, in the manufacture and assembly of the control parts carried bythe base 20, the present design represents numerous advantages. Thus thevalve body including the control head parts may be assembled complete.This is also true of the bracket assembly including the liapper andnozzle elements. Thereupon these subassemblies may be readily cooperatedand mounted as a unit on the base through the medium of the securingscrews 36. Similarly the movement assembly may be connected up with thehydron assembly and thereupon secured in unitary manner to the base 20.

, Referring now to the modified construction illustrated in Figures 6, 7and 9, the control assembly is there shown as connected with and mountedon another type of valve motor whose casing lacks the parts I4, I6characteristic of the Figures 1-4 construction. In the modifiedarrangement the base 20 has secured to its rear face a universal bracketmember generally indicated at |25. part |26 to which the rear of thebase 20 is secured as by cap screws |27. The plate part extends somewhatbeyond the side edge of the panel 20 and adjacent its end is providedwith the spaced jaws |28, |29, between which one of the yoke members |30of the motor is received. The depth cf the mouth provided between thejaws is such that the edge of the yoke member engages against the baseof the mouth, with the opposite edge of the yoke member being arrangedsubstantially ush with the outer jaw faces. The cross plate |3| isthereupon secured to the `aw faces as by bolts |32 in such manner as tospan the jaws and securely hold the bracket member |25 and hence thebase 20 to the motor yoke |30.

The valve stem |34 carries a transverse pin |35 against which the bellcrank arm 80 as previously described in connection with the Figures 1-4construction may engage. This arm 80 causes turning of the bell crankabout the axis of its axle member 82 also as. previously described.

Inasmuch as there is present in existing motor casing construction noextension air chamber I6,

This bracket member has a plate the bored plug screw 25, as previouslydescribed.

delivers to a passage |36 formed in a boss |31 on the bracket plate |26,into which boss is threaded the connecting nipple |38 of the air line|39 which delivers pressure air to the valve motor casing above thediaphragm thereof. By this arrangement pressure air from inlet 3| issupplied through the bored plug 25 and line |39 to the motor, at a valueor values such that the valve stem |34 takes up a position inproportional correspondence to the control force, in the same manner aspreviously described in relation to the Figures 1-4 construction.

The control instrumentalities carried by the base 20 in theconstructions above described may be protected by a cover |20 suitablycooperated with the base 20, as indicated in Figures 4 and 6, thus toprevent entry of dust to the various parts and mechanisms carried by thebase 20. This cover will be readily removable so that repair and/oradjustment of said parts may be made when and if necessary.

Referringstill to Figures 5 and 9, the control instrumentality may bearranged to translate position of the valve stem and its associatedmechanism into pressure by making the following changes: the line |39 isdisconnected from the valve motor and is connected through the pas sage91 (Figure l) to the bellows 95. Air supply from a suitable controlledsource is connected with the diaphragm motor at the point from which theline |39 was removed. In this manner, movement of the valve stern causesa pressure to be created in the bellows 95 which pressure varies inaccordance with the movement of the valve stem and its associated parts.

In Figure 9 this connection is diagrammatically shown. The control headand bellows 95 are now connected through passages 45, 46, 21, throughthe tube 25, through line |39 and passage 91. In this hook-up, thebellows 95 is reversed from its position as shown in Figure 1, toreceive pressure from the passage 91 instead of from the passage 98 andso that the expansion of the bellows will move the rack 'l5 to the leftinstead of to the right, as shown in Figure 1. As before, movement ofthe valve stem I3 moves the lever 80 about the axis 82 and moves thelong arm 13 of the movement assembly. The air pressure operating thevalve motor will now be coming from some control instrument such as wassupplying air to the bellows 95 when it was hooked up, as shown inFigures 1 through 5. Since the pressure existing in the bellows 95, whenhooked up as a pressure transmitter, is proportional to position of thestem I3, by connecting a pressure-indicating instrument to the bellows95 or to a line going to the bellows 95, the pressure therein may beread or recorded and calibrated in terms of valve stem position.

The operation of the instrument thus connected up may be described asfollows: Starting with the parts in equilibrium condition, the pressureon the valve motor will be constant and `the valve stem |3 stationary sothat the arm 80, the arm 13 and the arm 10 will all be stationary, andthe pressure existing in the bellows 95 will be proportional to theposition of the valve stem and suicient to keep the arm 10 so positionedas to maintain the flapper 63 tangent to the nozzle 64. Assuming nowthat the pressure on the valve motor is increased a certain amount, thiswill cause the valve stem to move downwardly and to take a new position.As it does so, the spring 9U reacting or. the arm 13 and on the bellcrank 05, 82 and 80 causes the free end of the arm 80 to follow thevalve stem movement, giving a counterclockwise rotation to the arms and85 of the bell crank and giving a clockwise rotation to the arm 13 ofthe movement assembly. This movement of the arm 13 is transmittedthrough the U-shaft 12 to the short arm 'I0 of the movement assemblywhich also moves in a clockwise direction, tending to permit the apper64 to cover the nozzle. This action of the flapper 64 on the nozzle 63tends to cause the pressure back of the nozzle to build up and to causethe bellows 55 connected with the nozzle through the passage 0| toexpand. This expansion of the bellows 55 starts the valve 52 moving tothe right, to resage 46 with the passage 45. This action starts reducingthe pressure in the bellows 85 which then starts collapsing under theaction ofthe spring IBI, and moves the raclr` 'l5 to the right. 'I'hismovement of the bellows and of the rack 15, acting through the short arm'I0 of the movement assembly, acts on the ilapper to maintain it tangentto the nozzle. The action and reaction of the parts balances out quicklyso that practically the pressure in the bellows 95 follows closely themovement of the valve stem I3.

As many changes could be made in carrying out the above constructions,without departing from the scope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense. v

I claim:

1. Control mechanism comprising, inl combination, an element to bepositioned, a pneumatic motor for actuating the element, a pressure airline tothe motor, a control head in the line, a control couple of thenozzle and pivoted ilapper type operatively related to the control head,a movement assembly,including an arm pivoted at one end to turn'about amovable axis and having its other end freely positionable, means forestablishing frictionlessly the position of the pivoting axis of the armin proportional correspondence with a control force, means forpositioning the free .end of lthe arm in proportional correspondencewith the position of the element being positioned comprising abell-crank assembly including spaced levers turnable about a iixed axis,one lever operatively following the position of the element andactuating the other lever to a position in correspondence therewith, andmeans urging the free end of the movement assembly arm into engagementwith the other lever of the bell-crank assembly, the movement assemblyincluding a second armmovable with the rst arm and having its free endengaging the flapper inv vsembly including a second arm movable with 125, through the passage 21 and through the pasthe ilrst arm and soarranged that the edge portion of the free end thereof may slidablyengage against a face of the apper whereby to position the flapper withreference to the nozzle.

3. Control mechanism comprising, in combination, an element to bepositioned, a pneumatic motor for actuating the element, a pressure airline to the motor, a control head in the line, a

control couple of the nozzle and pivoted ilapperl v type operativelyrelated to Ithe control head, ajy

movement assembly including an arm pivoted at. one end to turn about asettable axis and having its other end freely positionable, means forestablishing frictionlessly the position of the pivoting axis of .thearm in proportional correspondence with a control force, means forpositioning the free end of the arm in proportional correspondence withthe position of the velement being positioned comprisingsa bell-crankassembly including spaced Ievers turnable about a fixed' axis, one leveroperatively following 'the position of the elementl and actuating theother lever to a position in correspondence therewith, and means urgingthe free end of the movement assembly arm into engagement with the otherlever of the bell-crank assembly, the movement assembly including asecond arm movable with the ilrst arm and being arranged so vthat 4.Control mechanism comprising, in combination, an element tobepositioned, a pneumatic motor for actuating the element, and a controlassembly operatively related to the motor and including a mounting basecarried by the motor, al pressure air inlet formed in the base, the basehaving a pressure air passage therein communieating with the inlet anddelivering to the motor.

' a control head mounted on said base for controlling flow of pressureair through the passage,

-a movement assembly, means for setting frictionlessly one end of themovement assembly in proportional correspondence with a predeterminedvalue of control air pressure including a termediate its pivot and thevnozzle' andl operative Y to` position the ilapper with reference to thenozzle.

2. Control mechanism comprising, in combinai tion, an element to bepositioned, a pneumatic motor for actuating the element, a pressure airllne'to the motor, a control head in the line, a control couple voi" thenozzle and pivoted ilapper type operatively related to the control head,a movement assembly including an arm pivoted at one end to turn about amovable axis and having itsother end freely positionable. means forestablishing frictionlessly the position oi' the pivoting axis of thearm in proportional correspondence with a control force; means forpositioning the free end of the arm in proportional correspondence withthe position of the element being positioned comprising a bell-crankassembly including spaced levers turnable about a fixed axis, one leveroperatively following the position of the element andactuating the otherlever to a position in correspondence ,therewith and means urging'thefree end of the movement .assembly arm into engagement with the otherlever of the bell-crank assembly, the movementV ashydron-assemblycarried by the base, a control air inlet formed in the base andcommunicating with the hydron assembly, and a connection between thehydron and movement as- `sex'nblies, means extending through the baseand operative between the element to be positioned vand the other end ofthe movement assembly for positioning said other end in proportionalcorrespondence with the position of/ the/element, and a control couple'carried by the base in operative relation to the control head, thecontrol couple including a nozzle carried by the base and having an airconnection with the pressure air inlet and a pivoted apper associatedwith the nozzle, the movement assembly being operative to position theilapper with reference to the nozzle.

5. Control mechanism comprising, in combination, an element to bepositioned, a pneumatic motor for actuating the element, and a controlyassembly operatively related to the motor and including a mounting basecarried by the motor, a pressure air inlet formed in the base, the basevhaving a pressure air passage therein communicating' with the inlet anddelivering to the motor, a control head mounted on said base forcontrolling ow of pressure air through the passage, a movement assembly,means for frictionlessly setting one end of the assembly in protheassembly in proportional correspondence with the position of theelement, a control couple carried by the base and operatively relatedtothe control head, the couple comprising a nozzle having an airconnection with the pressure air inlet and a pivoted dapper, themovement assembly being operative to position the apper withreference tothe nozzle.

6. Control mechanism comprising, in combination, an element to bepositioned, a diaphragm motor for actuating the same including a casing,a control assembly mounted on a base and including a casing extensionsecured to the motor casing, a pressure air inlet-in the base. the basehaving a pressure air passage delivering to the casing extension, a.control head mounted on the base for controlling supply o! pressure airfrom the inlet through the passage to the motor casing, a movementassembly, means for frictionlessly setting one end of the assembly inproportional correspondence with a predetermined value of control airpressure including a hydron assembly carried by the base, a control airinlet in the base delivering to the hydron assembly, and a mechanicalconnection between the hydron assembly and the movement assembly, meansfor positioning the other end of the movement assembly in proportionalcorrespondence with the position of the element including a bell-cranklever mounted for turning on an axis l extending through the casingextension, one arm of the lever operating in the casing extension-tofollow the position ofthe element and thereby setting the position ofthe other arm thereof and the other end of the movement assemb1yand acontrol couple carried by the base and operatively related to thecontrol head, the couple comprising a nozzle having an air connection tothe pressure air inlet and a pivoted iiapper operatively related to thenozzle, the movement assembly being operative to position the dapperwith reference to the nozzle.

7. Control mechanism comprising, in combination, an element to bepositioned, a diaphragm motor for actuating the element, the motorincluding a yoke, a bracket having one end secured to the yoke, acontrol assembly including a mounting base carried by the other end ofthe bracket, a pressure air'inlet in the base, a pressure air.connection between the base'and the motor, the base having a pressureair passage from the inlet to the connection, a control head' carried bythe base for controlling flow of pres- 'sure air'through said passage, amovement assembly, means for setting frlctionlessly one end of theassembly in proportional correspondence with a predetermined value oi?vcontrol air pressure including a hydron assembly carried by the base,acontrol air inlet in the base Adelivering to the hydron assembly, meansfor position- -ing the'other end of the movement assembly in Y*associesa control couple carried by the base-and operatively related to thecontrol head, the control couple comprising a nozzle having an airconnection with the pressure air inlet and a pivoted ilapper, themovement assembly being operative to position the apper with referenceto the nozzle.

8. In a control mechanism for positioning an element movable by apneumatic motor, in combination, a supply and waste valve forcontrolling the pressure supplied to said motor, a `control coupleincluding a xed nozzle and pivoted baille for operating said supply andwaste valve. a movement assembly pivoted soley about a iloating axiscarried by the free end oi' a hydron expansible in accordance with acontrol force, means for positively driving the movement assembly aboutsaid axis including lever mecha nism movable about a iixed axis andhaving an arm which follows the position of the element, resilient meansfor urging said arm to follow the movement of the element, said'movementassembly being adapted to operate said :dapper whereby said motormaintains an exact relationship between said element and the conditionof expansion of said hydron, and means Ior adjusting the mechanicaladvantage between the movement assembly and the lever mechanism adjustthe relationship maintained by said motor between said element andhydron.

9. In apparatus for positioning an element in accordance with apneumatic pressure, in comblnation, a pneumatically operated diaphragmmoto.:` having a cover and a cap over the diaphragm, a mounting base, ahollow extension between said cap and cover and supporting said mountingbase, a source of air pressure, a non-restrictive passage in saidmounting base and connecting said air pressure and said hollowextension, valve means supported by said mounting base controlling theair pressure to said motor through said passage, a movement assembly foroperating said control means and so responsive to the position oi saidelement and to said pneumatic pressure as to continuously control theair supply to the valve motor as to cause it to correlate the positionof said element and said pneumatic pres-' l1. TheA combination, with adiaphragm motor having a cover over the diaphragm, oi' a cap se cured tosaid cover and housing a spring and rod movable .with the diaphragm. alaterally extending casing .between said cap and cover, controlmechanism supported by said casing, a bearins A supported by saidcasing, a crank having a shaft proportional correspondence with theposition of the element including a bell-cranklever turnable on 'an axisextending through the base, and 75 rotatable in said bearing and havingan arm movable. lwith said rod, said arm being housed in said casing,and an air passage between said control mechanism and the entrance ofsaid casing permitting -the flow-of air between said controlmechanismand said diaphragm.

.12. The combination, with a diaphragm motor having a diaphragm, arodand a yoke for supporting said diaphragm with respect to said rectlycontacting and adapted to operate said rod, of control mechanism mountedin the casing, means for supporting said casingon said yoke comprising ablade portion Aand a yoke porcomprising in combination a. hydron havinga free end' and expansible in accordance with the control pressure, apilot, valve including a port and a movable restriction thereto, asingle lever means pivotably carried by said hydron and dimovablerestriction, second lever means pivotable about a xed axis slidablycontacting `and adapted to operate said ilrst lever means, means"mechanically connecting said second lever means to move with saidelement and means for resiliently holding said single lever means, saidseoond lever means and said element in continuous operative contact,whereby said movable restriction is operated by the combined action ofsaid hydron and said element, and a valve of the supply-and-wastel typeoperated by said pilot valve for controlling passage of air'to and fromsaid motor.

LYMANCOOK.

